On Wed, Apr 29, 2015 at 01:57:59PM +0900, Minchan Kim wrote: > On Tue, Apr 28, 2015 at 03:24:42PM +0300, Vladimir Davydov wrote: > > @@ -69,6 +69,14 @@ There are four components to pagemap: > > memory cgroup each page is charged to, indexed by PFN. Only available when > > CONFIG_MEMCG is set. > > > > + * /proc/kpageidle. For each page this file contains a 64-bit number, which > > + equals 1 if the page is idle or 0 otherwise, indexed by PFN. A page is > > + considered idle if it has not been accessed since it was marked idle. To > > + mark a page idle one should write 1 to this file at the offset corresponding > > + to the page. Only user memory pages can be marked idle, for other page types > > + input is silently ignored. Writing to this file beyond max PFN results in > > + the ENXIO error. Only available when CONFIG_IDLE_PAGE_TRACKING is set. > > + > > How about using kpageflags for reading part? > > I mean PG_idle is one of the page flags and we already have a feature to > parse of each PFN flag so we could reuse existing feature for reading > idleness. Reading PG_idle implies clearing all pte references to make sure the page was not referenced via a pte. This means that exporting it via /proc/kpageflags would increase the cost of reading this file, even for users that don't care about PG_idle. I'm not sure all users of /proc/kpageflags will be fine with it. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>